Recently, among lens systems used for lens-shutter cameras, ones equipped with a zoom lens are becoming mainstream. Because this kind of zoom lens is required to be compact, two-group zoom lenses with a telescope-type refractive power arrangement are commercialized wherein, in order from the object side, the first lens group has positive refracting power and the second lens group has negative refracting power.
Furthermore, many lens systems are known where the number of lens elements is reduced and the optical performance is improved by using an aspherical surface as the lens element surface.
As for this kind of technology, zoom lenses having six lens elements in two groups are described in Japan patent publications H03-200913 and H06-82696. Also, zoom lenses having five lens elements in two groups are described in U.S. Pat. Nos. 5,663,838 and 5,687,028. However, there is a need for further improvements in miniaturization and cost reduction.